The present invention relates to piezoelectric resonators, particularly such resonators wherein energy trapping is implemented to reduce or eliminate spurious responses which result from interaction of an intended vibrational deformation in a portion of the piezoelectric arrangement with other portions of that arrangement.
A well known type of resonator structure includes a piezoelectric substrate having driving electrodes disposed on opposite surfaces thereof. When an AC source is applied across the electrodes, the substrate vibrates in accordance with the frequency of the AC source, as well as the piezoelectric and vibrational characteristics of the substrate. When the substrate surfaces extend beyond the electrodes, the extending portions thereof will tend to vibrate along with the portion thereof disposed between the electrodes. Because any vibrational deformation in those extending portions causes spurious responses from the resonator, energy trapping measures are usually taken to reduce or eliminate vibrational deformation in those portions. Such measures include techniques known as mass loading and contouring by which the natural frequencies of the extending portions and the portion between the electrodes are made to be different, so that vibrational deformation in the former will be reduced or eliminated when vibrational deformation occurs in the latter.